Managed Multi-Phase Operation

ABSTRACT

Systems and methods for maximum deviation multi-phase operation provide techniques for controlling voltage regulators and tap changers in a multi-phase system to operate within a maximum deviation window. The maximum deviation window comprises a low boundary value and a high boundary value. In an example embodiment, systems and methods provide techniques for setting the low boundary value and the high boundary value. In another example embodiment, systems and methods provide techniques for optimized power factor correction in a multi-phase system

RELATED APPLICATION

The present application claims priority to U.S. Provisional PatentApplication No. 61/605,643 titled “Managed Multi-Phase Operation” andfiled Mar. 1, 2012, the entire contents of which are incorporated hereinby reference.

TECHNICAL FIELD

The present disclosure relates generally to managed multi-phase voltageregulation and control in a multi-phase power system with a single phasecontrol and to systems, methods, and devices for managed multi-phasevoltage regulation and control with a single phase control.

BACKGROUND

Multi-phase power systems, which carry two or more alternating currents,are a common form of power distribution. The AC lines of a multi-phasepower system typically have a phase offset from the others. This allowsmulti-phase systems to transmit more power compared to single phasepower systems. A typical example of a multi-phase system is athree-phase electric power system. In a multi-phase system, a voltageregulator controller is used to maintain local operational control ofthe multiple connected single phase mechanisms that make up themulti-phase system. The voltage regulator controller may becommunicatively coupled to a voltage regulator, which comprises a tapchanger. The tap changer is capable of changing a tap position of thevoltage regulator, providing variable/stepped voltage output regulationassociated with a respective phase. Current multi-phase controlmethodology typically comprises a single mechanism for controllingmultiple phases, or a lock-step group of mechanisms to regulate themultiple phases. In certain circumstances, such as in the presence ofnon-uniformly balanced loads, such control methodology, may exacerbatesystem imbalance.

SUMMARY

In an example embodiment of the present disclosure, a method for maximumdeviation multi-phase operation comprises setting a low boundary valueof a maximum deviation window based on a first highest tap position of aplurality of tap changers, setting a high, boundary value of the maximumdeviation window based on a first lowest tap position of the pluralityof tap changers, and independently regulating, by a plurality of voltageregulator controllers, a respective plurality of voltages of arespective plurality of voltage regulators based on the tap positions ofthe plurality of tap changers.

In another example embodiment of the present disclosure, a system formaximum deviation multi-phase operation comprises a plurality of voltageregulators, a plurality of tap changers, in which each of the pluralityof tap changers is configured to change a tap position of one of theplurality of voltage regulators, and a plurality of voltage regulatorcontrollers is configured to set tap positions of the plurality of tapchangers. The system further comprises a controller coupled to at leastone of the plurality of voltage regulator controllers. The controller isconfigured to set a low boundary value of a maximum deviation windowbased on a first highest tap position of the plurality of tap changers,and set a high boundary value of the maximum deviation window based on afirst lowest tap position of the plurality of tap changers. Theplurality of voltage regulator controllers are configured to regulate arespective plurality of voltages of the plurality of voltage regulatorsbased on the tap positions of the plurality of tap changers.

In another example embodiment of the present disclosure, a method ofoptimized power factor correction comprises comparing a difference inmeasured power factors between two voltage regulators with apredetermined maximum difference, and when the difference is determinedto be greater than the maximum difference, storing the difference as aprevious difference in measured power factors. The method furthercomprises adjusting, by a controller, a tap position of one of thevoltage regulators, comparing, a second difference in measured, powerfactors between the two voltage regulators with the previous differencein measured power factors, and when the second difference in measuredpower factors is not less than the previous difference in measured powerfactors, returning, by the controller, the tap position of the one ofthe voltage regulators to a prior tap position.

In another example embodiment, a method of phase angle balancingincludes calculating an initial first phase angle, an initial secondphase angle, and an initial third phase angle. The initial first phaseangle, the initial second phase angle, and the initial third phase angleform an initial phase balance condition. The method further includesdetermining which of the initial first phase angle, the initial secondphase angle, and the initial third phase angle has the largest value,and adjusting an output voltage of a phase opposite the initial phaseangle having largest value.

In another example embodiment, a method of voltage delta balancingincludes calculating an initial first voltage delta, an initial secondvoltage, delta, and an initial third voltage delta. The initial firstvoltage delta, the initial second voltage delta, and the initial thirdvoltage delta form an initial voltage balance condition. The methodfurther includes determining which of the initial first voltage delta,the initial second voltage delta, and the initial, third voltage deltahas the largest value, and adjusting an output voltage of a phaseopposite the initial voltage delta having largest value.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the invention and the advantagesthereof, reference is now made to the following description, inconjunction with the accompanying figures briefly described as follows:

FIG. 1 illustrates a diagrammatic representation of a system for maximumdeviation multi-phase operation, in accordance with an exampleembodiment of the present disclosure;

FIG. 2 illustrates a flow chart of a first portion of a method formaximum deviation multi-phase operation, in accordance with an exampleembodiment of the present disclosure;

FIG. 3 further illustrates a flow chart of a second portion of themethod for maximum deviation multi-phase operation, in accordance withan example embodiment of the present disclosure;

FIG. 4 further illustrates a flow chart of a third portion of the methodfor maximum deviation multi-phase operation, in accordance with anexample embodiment of the present disclosure;

FIG. 5 illustrates a flow chart of another example embodiment of amethod for maximum deviation multi-phase operation, in accordance withan example embodiment of the present disclosure;

FIG. 6 illustrates a diagrammatic representation of a system foroptimized power factor correction, in accordance with an exampleembodiment of the present disclosure;

FIG. 7 illustrates a flow chart of a method for optimized power factorcorrection, in accordance with an example embodiment of the presentdisclosure;

FIG. 8 illustrates a flow chart of a method for voltage delta balancing,in accordance with an example embodiment of the present disclosure;

FIG. 9 illustrates a flow chart of a method for phase angle balancing,in accordance with an example embodiment of the present disclosure;

FIG. 10A illustrates a voltage delta vector diagram, in accordance withan example embodiment of the present disclosure; and

FIG. 10B illustrates a phase angle vector diagram, in accordance with anexample embodiment of the present disclosure.

The drawings illustrate only example embodiments of the invention andare therefore not to be considered limiting of its scope, as theinvention may admit to other equally effective embodiments. The elementsand features shown in the drawings are not necessarily to scale,emphasis instead being placed upon clearly illustrating the principlesof example embodiments of the present invention. Additionally, certaindimensions may be exaggerated to help visually convey such principles.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

In the following paragraphs, the present invention will be described infurther detail by way of example with reference to the attacheddrawings. In the description, well known components, methods, and/orprocessing techniques are omitted or briefly described so as not toobscure the invention. As used herein, the “present invention” refers toany one of the embodiments of the invention described herein and anyequivalents. Furthermore, reference to various feature(s) of the“present invention” is not to suggest that all embodiments must comprisethe referenced feature(s).

Among embodiments, some aspects of the present invention are implementedby a computer program executed by one or more processors, as describedand illustrated. As would be apparent to one having ordinary skill inthe art, the present invention may be implemented, at least in part, bycomputer-readable instructions in various forms, and the presentinvention is not intended to be limiting to a particular set or sequenceof instructions executed by the processor.

With regard to the process flow diagrams of FIGS. 2-4 and 6, it is notedthat the present invention may be practiced using an alternative orderof the steps illustrated in FIGS. 2-4 and 6. That is, the process flowsillustrated in FIGS. 2-4 and 6 are provided as examples only, and thepresent invention may, be practiced using process flows that differ fromthose illustrated. Additionally, it is noted that not all steps arerequired in every embodiment. In other words, one or more of the stepsmay be omitted or, replaced, without departing from the spirit and scopeof the invention. In alternative embodiments, steps may be performed indifferent orders, in parallel with one another, or omitted entirely,and/or certain additional steps may be performed without departing fromthe scope and spirit of the invention.

Turning now to the drawings, in which like numerals indicate likeelements throughout, example embodiments of the invention are describedin detail.

FIG. 1 illustrates an embodiment of a system 10 for maximum deviationmulti-phase operation of a plurality of voltage regulators with amulti-phase controller. The system 10 comprises a multi-phase controlsystem 100 and tap changers 132, 142, and 152, respectively, of voltageregulators 134, 144, and 154. The multi-phase control system 100comprises a memory 120 and voltage regulator controllers 130, 140, and150. Each of the voltage regulator controllers 130, 140, and 150 isconfigured to set a tap of a respective one of the tap changers 132,142, and 152, as illustrate. It is noted that the voltage regulatorcontrollers 130, 140, and 150 may be integrated together as, part of asingle controller or separate from each other. It is further noted thatthe memory 120 may reside, in part, within each of the voltage regulatorcontrollers 130, 140, and 150, or as, part of the single integratedcontroller, including each of the voltage regulator controllers 130,140, and 150.

In one embodiment, the voltage regulators 134, 144, and 154 each providea line voltage for a respective phase of a 3-phase power deliverysystem. However, the system 10 may comprise fewer or more voltageregulators, tap changers, and voltage regulator controllers. Further,each of the tap changers 132, 142, and 152 comprises a plurality of tapsby which a line voltage of one of the voltage regulators 134, 144, and154 may be selected and each of the voltage regulators 134, 144, and 154comprises a winding of a power transformer, as would be understood inthe art. The number of taps available for selection by each of the tapchangers 132, 142, and 152 may, range from 32 to 64 taps, for example,without limitation. One of ordinary skill in the art would appreciatethat the present invention may be embodied using various types ofvoltage regulators, various types of tap changers, and tap changershaving any number of tap positions available for selection.

Each of the voltage regulator controllers 130, 140, and 150 receives asense signal 138, 148, or 158 from a respective one of the windings ofthe respective voltage regulator 134, 144, and 154. Each sense signalcomprises a voltage and/or current sense signal based on a current lineoutput voltage and/or current of one of the windings of the respectivevoltage regulator 134, 144, and 154, according to a tap position set byone of the tap changers 132, 142, and 152, respectively. Each sensesignal 138, 148, and 158 further comprises feedback which permits thevoltage regulator controllers 130, 140, and 150 to determine the tapposition of the tap changers 132, 142, and 152. Each of the tap changersis controlled by a control signal 136, 146, or 156 from one of thevoltage regulator controllers 130, 140, or 150.

The voltage regulator controllers 130, 140, and 150 are communicativelycoupled together via a communications link. In one embodiment, one ofthe voltage regulator controllers 130, 140, and 150, acts as a leader,receives feedback from the other voltage regulator controllers 130, 140,and 150, and coordinates the operation of the other voltage regulatorcontrollers 130, 140, and 150, among other aspects. For example, asdescribed in further detail below, the leader controller is configuredto transmit a maximum deviation window comprising low and high tapposition boundary values among the voltage regulator controllers 130,140, and 150, and the voltage regulator controllers 130, 140, and 150are configured to operate the tap positions of the tap changers 132,142, and 152 within the maximum deviation window in one mode ofoperation. That is, in one mode of operation, the voltage regulatorcontrollers 130, 140, and 150 are configured to set the taps of the tap,changers 132, 142, and 152 within a permissible range of tap valuesdefined by the maximum deviation window. The voltage regulatorcontrollers 130, 140, and 150 are further configured to set the taps ofthe tap changers 132, 142, and 152 in view of the sense signals 138,148, and 158 and the permissible range of tap values. Additionally, thevoltage regulator controllers 130, 140, and 150 are configured totransmit information such as current tap position information to theleader controller, so that the leader controller may manage theoperation of the other voltage regulator controllers 130, 140, and 150in tandem.

The voltage regulator controllers 130, 140, and 150 are communicativelycoupled to a network 150 via communications link 102. An administrativeterminal 160 is also communicatively coupled to the network 150 viacommunications link 104. Using the communications links 102 and 104 andthe network 150, the administrative terminal 160 is able to communicatewith the voltage regulator controllers 130, 140, and 150. For example,the administrative computer 160 may be used to update parameters andsettings of the voltage regulator controllers 130, 140, and 150 tomanage the multi-phase operation of the voltage regulator controllers130, 140, and 150.

In general, the multi-phase control system 100 is configured to set alow boundary value of a maximum deviation window based on a currenthighest tap position of the plurality of tap changers 132, 142, and 152and a user-defined maximum deviation value, set a high boundary value ofthe maximum deviation window based on a current lowest tap position ofthe plurality of tap changers 132, 142, and 152 and the user-definedmaximum deviation value, and independently regulate, by the plurality ofvoltage regulator controllers 130, 140, and 150, voltages of theplurality of voltage regulators 134, 144, and 154 based on the tappositions of the plurality of tap changers 132, 142, and 152. Asdescribed herein, the maximum deviation window comprises a range ofacceptable, tap, positions for the plurality of tap changers 132, 142,and 152. In one mode of operation, multi-phase control system 100communicates the maximum deviation window among the voltage regulatorcontrollers 130, 140, and 150, and the voltage regulator controllers130, 140, and 150 independently regulate the voltages of the voltageregulators 134, 144, and 154 (via the tap changers), respectively,within the permissible tap positions defined by the maximum deviationwindow. For example, a leader controller of the voltage regulatorcontrollers 130, 140, and 150 may communicate the maximum deviationwindow among the controllers.

As described in further detail below, the maximum deviation window,MaxDevWin, comprises an array of high and low boundary values, {Low,High}. The high and low boundary values represent high and lowboundaries of tap positions of tap changers, when in a maximum deviationmulti-phase mode of operation. The multi-phase control system 100 mayset the high and low boundaries of the maximum deviation window withreference to the user defined maximum deviation value, MaxDevU, whichmay be defined by an administrator using the administrative terminal160, for example. At the outset of the maximum deviation mode ofoperation, the multi-phase control system 100 may also, set the high andlow boundaries of the maximum deviation window with reference to thehighest and lowest current tap positions of the voltage regulators beingmanaged, as described in further detail below.

In one aspect, the multi-phase control system 100 is configured to setboth the low and high boundary values of the maximum deviation window toan average of the highest and the lowest current tap positions of theplurality of tap changers, based on certain initial conditions of thesystem 10. The multi-phase control system 100 is further configured toset both the low boundary value and the high boundary value to anaverage of the highest and the lowest current tap positions of theplurality of tap changers 132, 142, and 152, based on other initialconditions of the system 10.

In other aspects, the multi-phase control system 100 is furtherconfigured to determine whether a difference between tap positions offirst and second of the plurality of tap changers 132, 142, and 152 anda difference between tap positions of second and third of the pluralityof tap changers 132, 142, and 152 are each equal to or greater than theuser-defined maximum deviation value, and decrement each of the high andlow boundary values of the maximum deviation window when it isdetermined that the differences are each equal to or greater than theuser-defined maximum deviation value, positions of two of the pluralityof tap changers 132, 142, and 152 are set to the low boundary value, andline voltages output by voltage regulators associated with the two ofthe plurality of tap changers are above a set voltage band. Themulti-phase control system 100 is further configured to determinewhether a difference between tap positions of first and second of theplurality of tap changers 132, 142, and 152 and a difference between tappositions of second and third of the plurality of tap changers 132, 142,and 152 are each equal to or greater than the user-defined maximumdeviation value, and increment each of the high and low boundary valuesof the maximum deviation window when it is determined that thedifferences are each equal to or greater than the user-defined maximumdeviation value, positions of two of the plurality of tap changers areset to the high boundary value, and line voltages output by voltageregulators associated with the two of the plurality of tap changers arebelow the set voltage band.

Turning to FIG. 2, a method for maximum deviation multi-phase operation200 is described. At step 202, the multi-phase control system 100determines whether multi-phase maximum deviation mode is to be enabled.With reference to the system 10, the determination may be made based onthe current status of the system 10, the current status or settings ofeach of the voltage regulator controllers, and, commands or parametersreceived from the administrative terminal 160, for example. When themulti-phase control system 100 determines that the conditions are set toenable maximum deviation multi-phase maximum deviation mode, the processproceeds to step 204. At step 204, the low and high boundary values ofthe maximum deviation window, MaxDevWin, are set by the multi-phasecontrol system 100. In one embodiment, the low and high values are set,to −16 and 16, respectively, but other initial values are within thescope of the disclosure. At step 206, MaxDevWin is communicated amongthe plurality of voltage regulator controllers 130, 140, and 150, and,at, step 208, each of the voltage regulator controllers 130, 140, and150 are set to activate maximum deviation multi-phase mode.

After entering maximum deviation multi-phase mode at step 208, a delayoccurs at step 210. The delay may be set by the multi-phase controlsystem 100 to allow any tap changes by the tap changers 132, 142, and152 to occur, as instructed by the voltage regulator controllers 130,140, and 150 after activation of maximum deviation multi-phase mode.Among embodiments, the amount of time for the delay at step 210 may varydepending upon design considerations. At step 212, the multi-phasecontrol system 100 sets the low boundary value of MaxDevWin, MaxDevL, tothe current highest tap position, TPIH, among the tap changers 132, 142,and 152 minus the user-defined maximum deviation value MaxDevU. Further,at step 214, the multi-phase control system 100 sets the high boundaryvalue of MaxDevWin, MaxDevH, to the current lowest tap position, TPIL,among the tap changers 132, 142, and 152 plus the user-defined maximumdeviation value MaxDevU.

At step 216, the multi-phase control system 100 determines whether thevalue of MaxDevL>MaxDevH. If MaxDevL is determined to be greater thanMaxDevH at step 216, the process proceeds to step 218 where both MaxDevLand MaxDevH are set by, the multi-phase control system 100 to an averageof the highest and lowest tap positions of the of the tap changers 132,142, and 152 when activating maximum deviation multi-phase mode. At step220, the multi-phase control system 100 sends MaxDevWin among thevoltage regulators 130, 140, and 150 and a delay in the process occursat step 222. After the delay at step 222, the multi-phase control system100 determines whether each of the tap changers 132, 142, and 152 havesettled to the tap defined by the average of the highest and lowest tappositions according to the direction of the voltage regulatorcontrollers 130, 140, and 150 at step 224. If the tap changers have notsettled, the process returns to step 220 and MaxDevWin is communicatedamong the voltage regulator controllers 130, 140, and 150, and theprocess delays at step 222.

On the other hand, if the tap changers 132, 142, and 152 have eachsettled to the tap defined by the average of the highest and lowest tappositions when activating maximum deviation multi-phase mode, theprocess proceeds to step 226. At step 226, the multi-phase controlsystem 100 increments MaxDevH by one with reference to FIG. 3, afterstep 226, the MaxDevWin (with the updated value of MaxDevH) iscommunicated among the voltage regulator controllers 130, 140, and 150at step 302, and the process delays at step 304. At step 306, themulti-phase control system 100 determines whether the difference betweenMaxDevH and MaxDevL is equal to the MaxDevU. If not, the processproceeds to step 308, where the multi-phase control system 100decrements MaxDevL by 1, MaxDevWin is communicated among the voltageregulator controllers 130, 140, and 150 at step 310, and the processdelays at step 312. At step 314, the multi-phase control system 100again determines whether the difference between MaxDevH and MaxDevL isequal to the MaxDevU and, if not, proceeds back to step 226 to incrementMaxDevH by one.

It is noted that, at steps 218, 220, 222, 224, 226, 302, 304, 306, 308,310, 312, and 314, the multi-phase control system 100 first collapsesand then re-opens the window of available tap positions defined byMaxDevWin, in response to an “error” condition being determined at step216. Particularly, if MaxDevL is determined to be greater than MaxDevHat step 216, the multi-phase control system 100 first collapses thewindow of available tap positions at step 218, waits for the voltageregulator controllers 130, 140, and 150 to set each tap position of thetap changers 132, 142, and 152 to the same tap position at steps 220,222, and 224, and then gradually re-opens the window of available tappositions at steps 226, 302, 304, 306, 308, 310, 312, and 314.

If, at step 216, the multi-phase control system 100 determines thatMaxDevL is less than MaxDevH, the process proceeds, to step 402,illustrated at FIG. 4. At step 402, MaxDevWin is communicated among thevoltage regulator controllers 130, 140, and 150 and the process delaysat step 404. After the delay at step 404, the multi-phase control system100 permits independent regulation of the voltage regulators 134, 144,and 154 by the voltage regulator controllers 130, 140, and 150.Particularly, at step 406, the voltage regulator controllers 130, 140,and 150 voltage-regulate the line voltage output of each of the voltageregulators 134, 144, and 154 using the tap changers 132, 142, and 152.The voltage regulator controllers 130, 140, and 150 may voltage-regulatethe line voltage of the voltage regulators 134, 144, and 154 based onthe voltage, current, and tap position sense feedback signals 138, 148,and 158.

At steps 408, 410, and 412, the multi-phase control system 100determines whether the difference between the tap positions of any twoof the tap changers 132, 142, and 152 is equal to or greater than theMaxDevU. If not, the process proceeds back to step 406, whereindependent voltage regulation continues. On the other hand, if themulti-phase control system 100 determines at steps 408, 410, and 412that the difference between the tap positions of any, two of the tapchangers 132, 142, and 152 is equal to or greater than the MaxDevU, theprocess proceeds to step 414. At step 414, the multi-phase controlsystem 100 determines whether positions of two of the tap changers 132,142, and 152 are set to the high boundary value MaxDevH and linevoltages output by voltage regulators associated with the two of theplurality of tap changers are below a set voltage band. If multi-phasecontrol system 100 determines that the conditions at step 414 are true,the process proceeds to step 418, where both MaxDevH and MaxDevL areincremented by one.

Alternatively, if the multi-phase control system 100 determines that theconditions at step 416 are false, the process proceeds to step 420,where the multi-phase control system 100 determines whether positions oftwo of the tap changers 132, 142, and 152 are set to the low boundaryvalue MaxDevL and line voltages output by voltage regulators associatedwith the two of the plurality of tap changers are above the set voltageband. If the multi-phase control system 100 determines that theconditions at step 416 are true, the process proceeds to step 420, whereboth MaxDevH and MaxDevL are decremented by one. After steps 418 or 420,the process proceeds to step 422, where MaxDevWin is communicated amongthe voltage regulator controllers 130, 140, and 150 and delays at step424. After the delay at step 424, the process proceeds back to step 406,where independent voltage regulation continues.

In another embodiment, the multi-phase control system 100 may be furtherconfigured to operate the voltage regulator controllers 130, 140, and150 in various modes of operation. For example, the multi-phase controlsystem 100 may control the voltage regulator controllers 130, 140, and150 in a type of enhanced leader/follower mode where historical tappositions are recorded over time. That is, the multi-phase controlsystem 100 may track the respective tap positions of the tap changers132, 142, and 152 by time of day or day of week, for example, and storethis information in the memory 120. When attempting to, address a systemvariation or troubleshoot system fluctuations, the multi-phase controlsystem 100 may refer to the historical, tap position information storedin the memory 120 to set taps of the voltage regulators 134, 144, and154 based on previous tap position(s) based on time of day or week, forexample. Based on this operation, if a loss of neutral wire is detected,a tap changer may be set to a tap position based on a historical tapposition during or after repair. Historical tap position data may bestored in the memory 120 in thirty minute increments, for example,without limitation. The multi-phase control system 100 may also,calculate a running average of tap positions over hours, days, or weeksof operation.

In another embodiment, the multi-phase control system 100 may operate ina mode of operation to average the line voltage of the voltageregulators 134, 144, and 154 within an allowable deviation. Should adifference in tap position between any regulators be within a definedallowable deviation, the multi-phase control system 100 may regulate toan average system voltage without exceeding, the allowable deviation.The multi-phase control system 100 may be further configured to operatewithin any mode of operation described herein during a user-defined timeperiod maintained by a timer.

In other aspects, the multi-phase control system 100 may permit one ofthe following additional modes of operation after expiration of a timed,mode of operation: tap to neutral mode, ganged operation mode, regulateto historical tap position mode. Tap to neutral mode may be defined bythe multi-phase control system 100 directing each of the tap changers132, 142, and 152 to tap to neutral upon expiration of the timed mode ofoperation. Ganged operation mode may be defined by the multi-phasecontrol system 100 locking all voltage regulators 134, 144, and 154 inganged mode (lock-step operation) based on an average voltagecalculation of a leader regulator upon expiration of the timed mode ofoperation. The regulate to historical tap position mode may be definedby the multi-phase control system 100 to regulate to historical tapposition data which was previously stored in the memory 120, asdescribed above, upon expiration of the timed mode of operation.

Deactivation of any of the modes described herein may be achieved byuser selectable options at either a control panel of one of the voltageregulator controllers 130, 140, and 150 or the administrative terminal160. Should one mode be deactivated, the voltage regulator controllers130, 140, and 150 may resume normal regulation or resume regulationbased another predefined mode.

Turning to FIG. 5, another embodiment of a method for maximum deviationmulti-phase operation, 500, is described. At step 502, the multi-phasecontroller 100 determines whether multi-phase maximum deviation mode isto be enabled. With reference to the system 10, the determination may bemade based on the current status of the system 10, the current status orsettings of each of the voltage regulator controllers 130, 140, and 150,and commands or parameters received from the administrative terminal160, for example. When the multi-phase controller 100 determines thatthe conditions are set to enable maximum deviation multi-phase maximumdeviation mode, the process proceeds to step 504. At step 504, the lowand high boundary values of the maximum deviation window, MaxDevWin, areset to the values of TPIL and TPIH, respectively. That is, at step 504,the multi-phase control system 100 sets the low boundary, value ofMaxDevWin, MaxDevL, to the current lowest tap position, TPIL, among thetap changers 132, 142, and 152 and sets the high boundary, value ofMaxDevWin, MaxDevH, to the current highest tap position, TPIH, among thetap changers 132, 142, and 152. At step 506, MaxDevWin is among theplurality of voltage regulator controllers 130, 140, and 150, and, ateach of the voltage regulator controllers 130, 140, and 150 are set toactivate maximum deviation multi-phase mode.

After entering maximum deviation multi-phase mode at step 508, a delayoccurs at step 509. The delay may, be set by the multi-phase controlsystem 100 to allow any tap changes by the tap changers 132, 142, and152 to occur, as instructed by the voltage regulator controllers 130,140, and 150 after activation of maximum deviation multi-phase mode.Among embodiments, the amount of time for the delay at step 509 may varydepending upon design considerations. At step 510, the multi-phasecontrol system 100 calculates the value of MaxDevM, defined asTPIH-TPIL. Specifically, the value of MaxDevM is equal to the value ofthe current highest tap position, TPIH, among the tap changers 132, 142,and 152 minus the value of the current lowest tap position, TPIL, amongthe tap changers 132, 142, and 152.

At step 512, the multi-phase control system 100 determines whether thevalue of MaxDevM is greater than the user-defined maximum deviationvalue MaxDevU. If MaxDevM is determined to be greater than MaxDevU atstep 512, the process proceeds to step 514 where the multi-phase controlsystem 100 sets the high boundary value of MaxDevWin, MaxDevH, toTPIH−1. After step 514, the process proceeds to step 516, whereMaxDevWin is communicated among the plurality of voltage regulatorcontrollers 130, 140, and 150. At step 518, the multi-phase controlsystem 100 again calculates the value of MaxDevM and, at step 520, themulti-phase control system 100 again determines whether the value ofMaxDevM is greater than the user-defined maximum deviation valueMaxDevU. If the value of MaxDevM is still greater than the user-definedmaximum deviation value MaxDevU at step 520, the process proceeds tostep 522, where the multi-phase control system 100 sets the low boundaryvalue of MaxDevWin, MaxDevL, to TPIL+1.

After step 522, the process proceeds to step 524, where MaxDevWin iscommunicated among the plurality of voltage regulator controllers 130,140, and 150. At step 526, the multi-phase control system 100 againcalculates the value of MaxDevM and, at step 528, the multi-phasecontrol system 100 again determines whether the value of MaxDevM isgreater than the user-defined maximum deviation value MaxDevU. If thevalue of MaxDevM is still greater than the user-defined maximumdeviation value MaxDevU at step 528, the process proceeds back to step514, where the multi-phase control system 100 reduces the current highboundary value of MaxDevWin, MaxDevH, by 1.

It is noted that steps 510, 512, 514, 516, 518, 520, 522, 524, 526, and528 seek to slowly bring the difference between the current highest TPIHand lowest TPIL tap positions among the tap changers 132, 142, and 152,MaxDevM, within the range defined by the user-defined maximum deviationvalue, MaxDevU. Especially when first activating maximum deviationmulti-phase mode, the value of MaxDevM may be greater than the value ofMaxDevU. In the method 500, this condition is identified at steps 512,520, and 528 (and later at step 536). It is again noted that, afteractivating maximum deviation multi-phase mode at step 508, each voltageregulator controllers 130, 140, and 150 controls and maintains the tapposition of its respective tap changer 132, 142, and 152 to be withinthe positions defined by the maximum deviation window MaxDevWin.Initially, because the maximum deviation window MaxDevWin is set to thecurrent highest TPIH and lowest TPIL tap positions among the tapchangers 132, 142, and 152 at step 504, the voltage regulatorcontrollers 130, 140, and 150 do not need to change tap positions.However, as the upper and lower boundaries MaxDevH and MaxDevL of themaximum deviation window MaxDevWin are incrementally confined at steps514 and 522, the voltage regulator controllers 130, 140, and 150 maychange tap positions, as necessary, to bring the tap positions of thetap changers 132, 142, and 152 within the range of permissible tappositions defined by MaxDevWin. In turn, the difference between thecurrent highest TPIH and lowest TPIL tap positions among the tapchangers 132, 142, and 152, MaxDevM, will reduce. In this manner, thevalue of MaxDevM will eventually converge to be equal to or less thanvalue of the user-defined maximum deviation value MaxDevU.

If the value of MaxDevM is determined to be equal to or less than theuser-defined maximum deviation value MaxDevU at steps 512, 520, or 528,the process proceeds to step 530, where a settling delay occurs at step530. The delay at step 530 is configurable to be the same as ordifferent than the delay at step 509. At step 532, the multi-phasecontrol system 100 reads the current tap position of each of the tapchangers 132, 142, and 152 and, at step 534, the values of MaxDevM,MaxDevH, and MaxDevL are calculated, retrieved, or determined. At step536, the multi-phase control system 100 determines whether the value ofMaxDevM is greater than the user-defined maximum deviation valueMaxDevU. If the value of MaxDevM is determined to be, greater than theuser-defined maximum deviation value MaxDevU at step 536, the processproceeds to step 514, as illustrated. Alternatively, if the value ofMaxDevM is determined to be equal to or less than, the user-definedmaximum deviation value MaxDevU at step 536, the process proceeds tostep 538 where MaxDevWin is communicated among the plurality of voltageregulator controllers 130, 140, and 150. Generally, step 538 may beconsidered to comprise a steady state where independent voltageregulation continues by the voltage regulator controllers 130, 140, and150.

At steps 540, 542, and 544, the multi-phase control system 100determines whether the difference between the tap positions of any twoof the tap changers 132, 142, and 152 is equal to or greater than theMaxDevU. If the multi-phase control system 100 determines at any ofsteps 540, 542, and 544 that the difference between the tap positions ofany two of the tap changers 132, 142, and 152 is equal to or greaterthan MaxDevU, the process proceeds to step 546. At step 546, themulti-phase control system 100 sets the MaxDevF flag, indicating thattap positions of the tap changers 132, 142, and 152 are set at thelimits defined by the user-defined maximum deviation value MaxDevU. Themulti-phase control system 100 also starts a timer, ModeSelectTimer, atstep 546. The process defined by the method 500 will exit to anotherpredefined routine if the timer ModeSelectTimer expires or overflowsand, generally, the timer ModeSelectTimer runs while the MaxDevF flag isset. The timer ModeSelectTimer may count up or down and may be set torun for a predetermined and configurable amount of time until directingan interrupt of the method 500, for example. In this manner, the timerModeSelectTimer will cause the process defined by the method 500 tointerrupt or end if the tap positions of the tap changers 132, 142, and152 are set at the limits defined by the user-defined maximum deviationvalue MaxDevU for an extended predetermined and configurable period oftime.

If the multi-phase control system 100 determines at steps 540, 542, and544 that no difference between the tap positions of any two of the tapchangers 132, 142, and 152 is equal to or greater than the MaxDevU, theprocess proceeds to step 558. At step 558, the multi-phase controlsystem 100 clears the MaxDevF flag and stops or resets the timerModeSelectTimer, and the process proceeds to step 530. Thus, if themulti-phase control system 100 determines at steps 540, 542, and 544that no difference between the tap positions of any two of the tapchangers 132, 142, and 152 is equal to or greater than the MaxDevU,generally, independent voltage regulation by the voltage regulatorcontrollers 130, 140, and 150 continues.

At step 548, the multi-phase control system 100 determines whetherpositions of two of the tap changers 132, 142, and 152 are set to thehigh boundary value MaxDevH and line voltages output by voltageregulators associated with the two of the plurality of tap changers arebelow a set voltage band. If multi-phase control system 100 determinesthat the conditions at step 548 are true, the process proceeds to step552, where both MaxDevH and MaxDevL are incremented by one.Alternatively, if the multi-phase control system 100 determines that theconditions at step 548 are false, the process proceeds to step 550,where the multi-phase control system 100 determines whether positions oftwo of the tap changers 132, 142, and 152 are set to the low boundaryvalue MaxDevL and line voltages output by voltage regulators associatedwith the two of the plurality of tap changers are above, the set voltageband. If the multi-phase control system 100 determines that theconditions at step 550 are false, the process returns to step 530.Alternatively, if the multi-phase control system 100 determines that theconditions at step 550 are true, the process proceeds to step 554, whereboth MaxDevH and MaxDevL are decremented by one. After steps 552 or 554,the process proceeds to step 556, where MaxDevWin is communicated amongthe voltage regulator controllers 130, 140, and 150 and the processproceeds to step 530 for continued independent voltage regulation by thevoltage regulator controllers 130, 140, and 150.

Turning to FIG. 6, a system 60 for optimized power factor correction isdescribed. The system 60 comprises a leader voltage regulator controller610, a follower voltage regulator controller 620, a voltage regulator630 of phase A of a first power system, a voltage regulator 640 of phaseA of a second power system, and a load 650. FIG. 6 illustrates aparallel connection among common phases “A” of two separate multi-phasepower delivery systems. In FIG. 6, line outputs from common phases oftwo different power systems are coupled, or connected in parallel todrive the load 650. In this configuration, the load 650 is supplied withpower from phase A of both the first and second power systems, which maybe necessary in cases where load 650 demands a large amount of power.The voltage regulators 630 and 640 are similar to the voltage regulatorsdescribed with reference to FIG. 1. Each voltage regulator 630 and 640regulates a line voltage of phase A of a respective multi-phase powersystem.

The leader and follower voltage regulator controllers 610 and 620 areconfigured to regulate line output voltages of phase A of the first andsecond power systems, respectively, using the first and second voltageregulators 630 and 640. The leader and follower voltage regulatorcontrollers 610 and 620 may regulate the output voltages by changingtaps of tap changers of the first and second voltage regulators 630 and640, as necessary, based on voltage and/or current sense feedbacksignals. In the configuration illustrated in FIG. 6, the leader andfollower voltage regulator controllers 610 and 620 are communicativelycoupled and the leader voltage regulator controller 610 directs thefollower voltage regulator controller 620. For example, the leadervoltage regulator controller 610 may be programmed with a voltage to beregulated for the load 650 and coordinate the voltage control of thefollower voltage regulator controller 620 accordingly.

Because the line outputs from the voltage regulators 630 and 640 arecoupled together to drive the load 650 as illustrated in FIG. 6,circulating current may flow between the voltage regulators 630 and 640if an imbalance exists between them. The imbalance may exist due todifferences in properties of the respective voltage regulators 630 and640, such as impedance mismatches. This imbalance may be identified bythe voltage regulator controllers 610 and 620, at least in part, by ameasure of the difference in power factors of power delivered by each ofthe voltage regulators 630 and 640. Thus, the leader and followervoltage regulator controllers 610 and 620 are configured to measure thepower factors of power delivered by each of the voltage regulators 630and 640 using voltage and current sense signals provided by the voltageregulators 630 and 640. As understood in the art, power factor isdefined as the ratio between the real power delivered and the absolutevalue of complex power delivered. Ideally, the power factor for powerdelivered by each of the voltage regulators 630 and 640 would be 1.

When the power factor of the first voltage regulator 630 is differentthan the power factor of the second voltage regulator 640, circulatingcurrent will flow between the two regulators, which causes energy lossand, perhaps, system damage. One way to correct the difference in powerfactor is by changing tap positions of tap changers of the voltageregulator controllers 630 and 640.

In this context, a method 700 of optimized power factor correction isdescribed with reference to FIG. 7. At the outset, it is noted that thesteps of the method 700 may be performed by the leader voltage regulatorcontroller 610, the follower voltage regulator controller 620, or acombination of the leader and follower voltage regulator controllers 610and 620. At step 710, a difference in measured power factors between thepower output by the first and second voltage regulators 630 and 640 iscompared to a user-defined maximum difference. For example, if the powerfactor of the power output by the first voltage regulator 630 ismeasured to be 0.95, the power factor of the power output by the secondvoltage regulator 640 is measured to be 0.8, and the user definedmaximum difference is 0.1, then the condition at step 710 is true, andthe process proceeds to step 720.

At step 720, an average of the line voltages output by each phase iscalculated and compared with a user-defined voltage set for regulation.If the average voltage is equal to or greater than the set voltage forregulation, the process proceeds to step 722, where the difference inpower factor measured between the power output by the first and secondvoltage regulators 630 and 640 is stored in memory (i.e., as N, forexample). At step 724, the follower voltage regulator controller 620commands the second voltage regulator 640 to a lower tap position. Atstep 726, the difference in power factor is compared with the previousvalue stored in memory, to determine if it is lower than the previousvalue. In other words, after lowering the tap position of the secondvoltage regulator 640, the difference in power factor is again measuredbetween the power output by the first and second voltage regulators 630and 640 and compared with the difference in power factor measured beforethe tap position of the second voltage regulator 640 was lowered. If itis lower, the process proceeds back to step 710 to determine whether thenew difference in power factor is less than the user-defined maximum.

Alternatively, at step 720, if the average voltage is not equal to orgreater than the set voltage for regulation (i.e., less than), theprocess proceeds to step 723, where the difference in power factormeasured between the power output by the first and second voltageregulators 630 and 640 is stored in memory (i.e., as Δ1, for example).At step 725, the leader voltage regulator controller 610 commands thefirst voltage regulator 630 to a higher tap position. It is noted that,as compared to step 724, it is acceptable to command the first voltageregulator 630 to a higher tap position at step 725, because the averagevoltage was not found to be equal to or greater than the set voltage forregulation at step 720. At step 727, the difference in power factor iscompared with the previous value stored in memory, to determine if it islower than the previous value. If it is lower, the process proceeds backto step 710 to determine whether the new difference in power factor isless than the user-defined maximum.

Returning to step 726, if the difference in power factor is comparedwith the previous value and determined to be higher than the previousvalue, the process proceeds to step 728 where the follower voltageregulator controller 620 commands the second voltage regulator 640 toincrease tap positions. It is noted that, because the difference inpower factor after the tap-down command at step 724 was not determinedat step 726 to be less than the difference stored at step 722, thetap-down command at step 724 is undone by the tap-up command at step728, effectively returning the system to its original state. The processthen proceeds, to step 740 where a corresponding process of steps isperformed.

Similarly, returning to step 727, if the difference in power factor iscompared with the previous value and determined to be higher than theprevious value, the process proceeds to step 729 where the leadervoltage regulator controller 610 commands the first voltage regulator630 to decrease tap positions. It, is noted that, because the differencein power factor after the tap-up command at step 725 was not determinedat step 727 to be less than the difference stored at step 723, thetap-up command at step 725 is undone by the tap-down command at step729, effectively returning the system to its original state. The processthen proceeds to step 740 where a corresponding process of steps isperformed.

The process of steps 740 and 742-749 are similar to steps 720 and722-729, respectively, except that, at step 744, the leader voltagecontroller regulator controller 610 commands the first voltage regulatorcontroller 630 to increase tap positions at step 744 rather than thefollower voltage controller regulator controller 620 commanding thesecond voltage regulator controller 640 to increase tap positions (as atstep 724). Thus, steps 740 and 742-749 represent an opposite approach tothe reduction of the power factor difference as compared to steps 720and 722-729.

In alternative embodiments of method 700, the process may proceeddirectly to step 740 rather than 720 after the decision at step 710 andonly return to step 720 if steps 740 and 742-749 fail to reduce thedifference in power factor. In another embodiment, a record of successof power factor difference reduction by steps 720 and 722-729 and arecord of success of power factor difference reduction by steps 720 and722-729 may be stored. In this case, after step 710, the process mayproceed to either step 720 or 740 based on a prior history of power,factor difference reduction success, determined with reference to thestored records.

Referring again to FIG. 1, in certain example embodiments, themulti-phase control system 100 is able to monitor and control voltagedeltas and phase angles between the three phases being regulated bycontrolling each of the tap changers 132, 142, and 152 independently. Asdiscussed above, the sense signals 138, 148, and 158 provide feedbackfrom the respective voltage regulators 134, 144, and 154 to theregulator controllers 130, 140, and 150. In certain example embodiments,the sense signals 138, 148, and 158 each include data regarding thewaveshapes of the respective phase. The waveshapes of the three phasescan be compared to each other to calculate a voltage delta and a phaseangle between each of the three phases. Thus, one or more of the threerespective tap changers 132, 142, and 152 can be independentlycontrolled to adjust and correct and/or improve voltage delta and phaseangle balance.

FIG. 8 illustrates a method of monitoring and controlling voltage deltasbetween phases in accordance with an example embodiment of thedisclosure. FIG. 10A illustrates a vector diagram of the three phases134, 144, and 154, and respective voltage deltas 1002, 1004, and 1006between the three phases. As discussed above, the regulator controllers130, 140, and 150 receive sense signals 138, 148, and 158 which containdata regarding the voltages of the respective phases. Referring to FIGS.8 and 10A, in step 802 of the monitoring and control method, themulti-phase control system 100 uses this data to calculate an initialvoltage delta or difference between each of the phases. For example, theinitial voltage difference between the first phase 134 and the secondphase 144 may be designated as delta 1₀ 1002, the initial voltagedifference between the second phase 144 and the third phase 154 may bedesignated as delta 2₀ 1004, and the initial voltage difference betweenthe third phase 154 and the first phase 134 may be designated as delta3₀ 1006. In step 804, the largest delta value is determined. In step806, the output voltage of the phase or voltage regulator 134, 144, 154opposite of the largest delta value is adjusted. For example, if thelargest delta value is delta 1₁ 1002, which denotes the voltagedifferential between the first 134 and second 144 phases, then the tapposition of the voltage regulator corresponding to the third phase 154is adjusted to adjust the output voltage of the third phase.

Subsequently, in step 808, new voltage differentials (i.e., deltas) arecalculated, and the new deltas may be denoted as delta 1₁, delta 2₁, anddelta 3₁, respectively. In step 810, the new deltas are compared todetermine if the voltage balance between the new deltas (delta 1₁, delta2₁, and delta 3₁,) is better than the balance between the initial deltas(delta 1₀, delta 2₀, and delta 3₀,). If the balance is indeed better,then the process is repeated from step 802 until the balance between thenew deltas is not better than the initial deltas. When the balance isnot better, the process goes to step 812, where the latest voltageregulator adjustment is undone, putting the system into an optimizedvoltage balance condition between the three phases. Thus, in step 814,the current voltage regulator settings are maintained.

In certain example embodiments, the multi-phase control system 100periodically reconfirms that the system is in the optimized voltagedelta balance condition. In such example embodiments, the methodincludes step 816, in which it is determined whether or, not, apredetermined period of time has passed. If the predetermined period oftime has passed, which means that it is time to reconfirm the optimizedstate, the method is repeated from step 802. If the predetermined periodof time has not passed, then the current voltage, regulator settings aremaintained, as in step 814. The example method illustrated in FIG. 8 issimply one approach to balancing the voltage deltas in a three-phasesystem. In alternate embodiments, certain of the steps illustrated inthe example method of FIG. 8 may be altered or removed. Likewise, asimilar method can be applied to other types of multi-phase controlsystems.

FIG. 9 illustrates a method of monitoring and controlling phase anglesbetween phases in accordance with an example embodiment of thedisclosure. FIG. 10B illustrates a vector diagram of the three phases134, 144, and 154, and respective phase angles 1012, 1014, and 1016between the three phases. Referring to FIGS. 9 and 10B, in step 902, themulti-phase control system uses measured data 138, 148, and 158 from theregulator controllers to calculate an initial set of phase anglesassociated with the three phases. For example, the initial phase anglebetween the first phase 134 and the second phase 144 may be designatedas phase angle 1₀ 1012, the initial phase angle between the second phase144 and the third phase 154 may be designated as phase angle 2₀ 1014,and the initial phase angle between the third phase 154 and the firstphase 134 may be designated as phase angle 3₀ 1016. In step 904, thelargest phase angle is determined. In step 906, the output voltage ofthe voltage regulator 134, 144, 154 opposite of the largest phase angleis adjusted. For example, if the largest phase angle is phase angle 1₀1012, which denotes the phase angle between the first 134 and second 144phases, then the tap position of the voltage regulator corresponding tothe third phase 154 is adjusted to adjust the output voltage of thethird phase 154.

Subsequently, in step 908, new phase angles are calculated, and the newphase angles may be denoted as phase, angle 1₁, phase angle 2₁, andphase angle 3₁, respectively. In step 910, the new phase angles arecompared to determine if the phase angle balance between the new phaseangles (phase angle 1₁, phase angle 2₁, and phase angle 3₁,) is betterthan the balance between the initial phase angles (phase angle 1₄, phaseangle 2₀, and phase angle 3₀,). If the balance is indeed better, thenthe process is repeated from step 902 until the balance between the newphase angle is not better than the initial phase angle. When the balanceis not better, the process goes to step 912, where the latest voltageregulator adjustment is undone, putting the system into an optimizedphase angle balance condition between the three phases. Thus, in step914, the current voltage regulator settings are maintained.

In certain example embodiments, as similarly discussed above, themulti-phase control system 100 periodically reconfirms that the systemis in the optimized phase angle balance condition in step 916. Theexample method illustrated in FIG. 9 is simply one approach to balancingthe phase angles in a three-phase system. In alternate embodiments,certain of the steps illustrated in the example method of FIG. 9 may bealtered or removed. Likewise, a similar method can be applied to othertypes of multi-phase control systems.

In certain example embodiments, controlling of the voltage regulators134, 144, and 154 for either voltage delta or phase angle balancing isperformed by the multi-phase control system 100 automatically as apresent control scheme. In certain example embodiments, controlling ofthe voltage regulators 134, 144, and 154 is performed manually by anoperator when it is determined that one or more of the tap changers 132,142, and 152 should be adjusted to bring about a better voltage delta orphase angle balance. In certain example embodiments, the operator mayset additional voltage settings for each of the three phases, includingbandwidth and time delay settings, allowing for phase angledifferentiation.

Although embodiments of the present invention have been described hereinin detail, the descriptions are by way of example. The features of theinvention described herein are representative and, in alternativeembodiments, certain features and elements may be added or omitted.Additionally, modifications to aspects of the embodiments describedherein may be made by those skilled in the art without departing fromthe spirit and scope of the present invention defined in the followingclaims, the scope of which are to be accorded the broadestinterpretation so as to encompass modifications and equivalentstructures.

What is claimed is:
 1. A method for maximum deviation multi-phaseoperation, comprising: setting a low boundary value of a maximumdeviation window based on a first highest tap position of a plurality oftap changers; setting a high boundary value of the maximum deviationwindow based on a first lowest tap position of the plurality of tapchangers; and independently regulating, by a plurality of voltageregulator controllers, a respective plurality of voltages of arespective plurality of voltage regulators based on the tap positions ofthe plurality of tap changers.
 2. The method of claim 1, wherein thefirst highest tap position comprises a current highest tap position, andwherein the first lowest tap position comprises a current lowest tapposition.
 3. The method of claim 1, comprising: setting the low boundaryvalue of the maximum deviation window based on the first highest tapposition of the plurality of tap changers and a user-defined maximumdeviation value; and setting the high boundary value of the maximumdeviation window based on the first lowest tap position of the pluralityof tap changers and the user-defined maximum deviation value.
 4. Themethod of claim 3, comprising: determining whether a difference betweentap positions of a first tap changer and a second tap changer of theplurality of tap changers and a difference between tap positions of thesecond tap changer and a third tap changer of the plurality of tapchangers are each equal to or greater than the user-defined maximumdeviation value; decrementing each of the high and low boundary valuesof the maximum deviation window when it is determined that thedifferences are each equal to or greater than the user-defined maximumdeviation value, positions of two of the plurality of tap changers areset to the low boundary value, and line voltages output by voltageregulators associated with the two of the plurality of tap changers areabove a set voltage band; and incrementing each of the high and lowboundary values of the maximum deviation window when it is determinedthat the differences are each equal to or greater than the user-definedmaximum deviation value, positions of two of the plurality of tapchangers are set to the high boundary value, and line voltages output byvoltage regulators associated with the two of the plurality of tapchangers are below the set voltage band.
 5. The method of claim 2,further comprising: when the low boundary value is greater than the highboundary value after setting the low and high boundary values, settingboth the low boundary value and the high boundary value to an average ofthe highest and the lowest current tap positions of the plurality of tapchangers.
 6. The method of claim 5, further comprising: after settingboth the low boundary value and the high boundary value to the averageof the highest and the lowest current tap positions of the plurality oftap changers, incrementing the high boundary value of the maximumdeviation window and decrementing the low boundary value of the maximumdeviation window until the maximum deviation window is equal to theuser-defined maximum deviation value.
 7. The method of claim 1, furthercomprising: transmitting the low boundary value and the high boundaryvalue from a lead voltage regulator controller to the plurality ofvoltage regulator controllers, wherein the lead voltage regulatorcontroller is selected from the plurality of voltage regulatorcontrollers.
 8. The method of claim 1, further comprising: controllingthe tap positions of the plurality of tap changers to operate within thelow boundary value and the high boundary value.
 9. A system for maximumdeviation multi-phase operation, comprising: a plurality of voltageregulators; a plurality of tap changers, each of the plurality of tapchangers configured to change a tap position of one of the plurality ofvoltage regulators; a plurality of voltage regulator controllersconfigured to set tap positions of the plurality of tap changers; and acontroller coupled to at least one of the plurality of voltage regulatorcontrollers, the controller configured to: set a low boundary value of amaximum deviation window based on a first highest tap position of theplurality of tap changers; and set a high boundary value of the maximumdeviation window based on a first lowest tap position of the pluralityof tap changers, wherein the plurality of voltage regulator controllersare configured to regulate a respective plurality of voltages of theplurality of voltage regulators based on the tap positions of theplurality of tap changers.
 10. The system for maximum deviationmulti-phase operation of claim 9, wherein the first highest tap positioncomprises a current highest tap position, and where the first lowest tapposition comprises a current lowest tap position.
 11. The system formaximum deviation multi-phase operation of claim 9, wherein thecontroller is further configured to: set the low boundary value of amaximum deviation window based on the first highest tap position of theplurality of tap changers and a user-defined maximum deviation value;and set the high boundary value of the maximum deviation window based onthe first lowest tap position of the plurality of tap changers and theuser-defined maximum deviation value.
 12. The system for maximumdeviation multi-phase operation of claim 11, wherein the controller isfurther configured to: determine whether a difference between tappositions of a first tap changer and a second tap changer of theplurality of tap changers and a difference between tap positions of thesecond tap changer and a third tap changer of the plurality of tapchangers are each equal to or greater than the user-defined maximumdeviation value; decrement each of the high and low boundary values ofthe maximum deviation window when it is determined that the differencesare each equal to or greater than the user-defined maximum deviationvalue, positions of two of the plurality of tap changers are set to thelow boundary value, and line voltages output by voltage regulatorsassociated with the two of the plurality of tap changers are above a setvoltage band; and increment each of the high and low boundary values ofthe maximum deviation window when it is determined that the differencesare each equal to or greater than the user-defined maximum deviationvalue, positions of two of the plurality of tap changers are set to thehigh boundary value, and line voltages output by voltage regulatorsassociated with the two of the plurality of tap changers are below theset voltage band.
 13. The system for maximum deviation multi-phaseoperation of claim 9, wherein the plurality of voltage regulatorcontrollers control the tap positions of the plurality of tap changersto operate within the low boundary value and the high boundary value.14. The system for maximum deviation multi-phase operation of claim 9,wherein the plurality of voltage regulator controllers comprise a firstvoltage regulator controller, a second voltage regulator controller, anda third voltage regulator controller, wherein the plurality of tapchangers comprise a first tap changer associated with the first voltageregulator controller, a second tap changer associated with the secondvoltage regulator controller, and a third tap changer associated withthe third voltage regulator controller, and wherein the first regulatorcontroller is configured to transmit the low boundary value and the highboundary value to the second and third voltage regulator controllers.15. The system for maximum deviation multi-phase operation of claim 14,wherein the second and third voltage regulator controllers areconfigured to transmit the tap positions of the second and third tapchangers, respectively, to the first voltage regulator controller. 16.The system for maximum deviation multi-phase operation of claim 9,comprising: an administrative terminal configured to control and/ormonitor the plurality of voltage regulator controllers.
 17. A method ofoptimized power factor correction, comprising, comparing a difference inmeasured power factors between two voltage regulators with apredetermined maximum difference; when the difference is determined tobe greater than the maximum difference, storing the difference as aprevious difference in measured power factors; adjusting, by acontroller, a tap position of one of the voltage regulators; comparing asecond difference in measured power factors between the two voltageregulators with the previous difference in measured power factors; andwhen the second difference in measured power factors is not less thanthe previous difference in measured power factors, returning, by thecontroller, the tap position of the one of the voltage regulators to aprior tap position.
 18. The method of optimized power factor correctionof claim 17, comprising: comparing an average line voltage valueassociated with the two voltage regulators with a set voltage regulationvalue; and when the average line voltage value is greater than or equalto the set voltage regulation value, set a first voltage regulator ofthe two voltage regulators to a lower tap position.
 19. The method ofoptimized power factor correction of claim 18, comprising: when theaverage line voltage value is not greater than or equal to the setvoltage regulation value, set a second voltage regulator of the twovoltage regulators to a higher tap position.
 20. The method of optimizedpower factor correction of claim 17, wherein the predetermined maximumdifference is a user-defined maximum deviation value.
 21. A method ofphase angle balancing, comprising: calculating an initial first phaseangle, an initial second phase angle, and an initial third phase angle,wherein the initial first phase angle, the initial second phase angle,and the initial third phase angle form an initial phase balancecondition; determining which of the initial first phase angle, theinitial second phase angle, and the initial third phase angle has thelargest value; and adjusting an output voltage of a phase opposite theinitial phase angle having largest value.
 22. The method of phase anglebalancing of claim 21, comprising: calculating a new first phase angle,a new second phase angle, and a new third phase angle, wherein the newfirst phase angle, the new second phase angle, and the new third phaseangle form a new balance condition; determining if the new balancecondition is better than the initial balance condition; when the newbalance condition is better than the initial balance condition:determining which of the new first phase angle, the new second phaseangle, and the new third phase angle has the largest value; andadjusting the output voltage of the phase opposite the new phase anglehaving the largest value; and when the new balance condition is notbetter than the initial balance condition, undoing a latest adjustment.23. A method of voltage delta balancing, comprising: calculating aninitial first voltage delta, an initial second voltage delta, and aninitial third voltage delta, wherein the initial first voltage delta,the initial second voltage delta, and the initial third voltage deltaform an initial phase balance condition; determining which of theinitial first voltage delta, the initial second voltage delta, and theinitial third voltage delta has the largest value; and adjusting anoutput voltage of a phase opposite the initial voltage delta havinglargest value.
 24. The method of voltage delta balancing of claim 23,comprising: calculating a new first voltage delta, a new second voltagedelta, and a new third voltage delta, wherein new first voltage delta,the new second voltage delta, and the new third voltage delta form a newbalance condition; determining if the new balance condition is betterthan the initial balance condition; when the new balance condition isbetter than the initial balance condition: determining which of the newfirst voltage delta, the new second voltage delta, and the new thirdvoltage delta has the largest value; and adjusting the output voltage ofthe phase opposite the new voltage delta having the largest value; andwhen the new balance condition is not better than the initial balancecondition, undoing a latest adjustment.